.. _overview:

=====================

Installation overview

=====================

Some overview and some details that can help understanding the options when

installing Kallithea.

1. **Prepare environment and external dependencies.**

    Kallithea needs:

    * A filesystem where the Mercurial and Git repositories can be stored.

    * A database where meta data can be stored.

    * A Python environment where the Kallithea application and its dependencies

      can be installed.

    * A web server that can host the Kallithea web application using the WSGI

      API.

2. **Install Kallithea software.**

    This makes the ``kallithea-cli`` command line tool available.

3. **Create low level configuration file.**

    Use ``kallithea-cli config-create`` to create a ``.ini`` file with database

4. **Populate the database.**

    Use ``kallithea-cli db-create`` with the ``.ini`` file to create the

    database schema and insert the most basic information: the location of the

    repository store and an initial local admin user.

5. **Configure the web server.**

    The web server must invoke the WSGI entrypoint for the Kallithea software

    using the ``.ini`` file (and thus the database). This makes the web

    application available so the local admin user can log in and tweak the

    configuration further.

6. **Configure users.**

    The initial admin user can create additional local users, or configure how

    users can be created and authenticated from other user directories.

See the subsequent sections, the separate OS-specific instructions, and

:ref:`setup` for details on these steps.

Python environment

------------------

**Kallithea** is written entirely in Python_ and requires Python version

3.6 or higher.

Given a Python installation, there are different ways of providing the

environment for running Python applications. Each of them pretty much

corresponds to a ``site-packages`` directory somewhere where packages can be

installed.

Kallithea itself can be run from source or be installed, but even when running

from source, there are some dependencies that must be installed in the Python

environment used for running Kallithea.

- Packages *could* be installed in Python's ``site-packages`` directory ... but

  that would require running pip_ as root and it would be hard to uninstall or

  upgrade and is probably not a good idea unless using a package manager.

- Packages could also be installed in ``~/.local`` ... but that is probably

  only a good idea if using a dedicated user per application or instance.

- Finally, it can be installed in a virtualenv. That is a very lightweight

  "container" where each Kallithea instance can get its own dedicated and

  self-contained virtual environment.

We recommend using virtualenv for installing Kallithea.

- The Kallithea source repository can be cloned and used -- it is kept stable and

  can be used in production. The Kallithea maintainers use the development

  branch in production. The advantage of installation from source and regularly

  updating it is that you take advantage of the most recent improvements. Using

  it directly from a DVCS also means that it is easy to track local customizations.

  Running ``pip install -e .`` in the source will use pip to install the

  necessary dependencies in the Python environment and create a

  ``.../site-packages/Kallithea.egg-link`` file there that points at the Kallithea

  source.

- Kallithea can also be installed from ready-made packages using a package manager.

  The official released versions are available on PyPI_ and can be downloaded and

  installed with all dependencies using ``pip install kallithea``.

  With this method, Kallithea is installed in the Python environment as any

  other package, usually as a ``.../site-packages/Kallithea-X-py3.8.egg/``

  directory with Python files and everything else that is needed.

  (``pip install kallithea`` from a source tree will do pretty much the same

  but build the Kallithea package itself locally instead of downloading it.)

.. note::

   Kallithea includes front-end code that needs to be processed first.

   The tool npm_ is used to download external dependencies and orchestrate the

   processing. The ``npm`` binary must thus be available.

Web server

----------

Kallithea is (primarily) a WSGI_ application that must be run from a web

server that serves WSGI applications over HTTP.

Kallithea itself is not serving HTTP (or HTTPS); that is the web server's

responsibility. Kallithea does however need to know its own user facing URL

(protocol, address, port and path) for each HTTP request. Kallithea will

usually use its own HTML/cookie based authentication but can also be configured

to use web server authentication.

There are several web server options:

- Kallithea uses the Gearbox_ tool as command line interface. Gearbox provides

  ``gearbox serve`` as a convenient way to launch a Python WSGI / web server

  from the command line. That is perfect for development and evaluation.

  Actual use in production might have different requirements and need extra

  work to make it manageable as a scalable system service.

- `Apache httpd`_ can serve WSGI applications directly using mod_wsgi_ and a

  simple Python file with the necessary configuration. This is a good option if

  Apache is an option.

- IIS_ can also server WSGI applications directly using isapi-wsgi_.

- A `reverse HTTP proxy <https://en.wikipedia.org/wiki/Reverse_proxy>`_

  can be put in front of another web server which has WSGI support.

  Such a layered setup can be complex but might in some cases be the right

  option, for example to standardize on one internet-facing web server, to add

  encryption or special authentication or for other security reasons, to

  provide caching of static files, or to provide load balancing or fail-over.

  Nginx_, Varnish_ and HAProxy_ are often used for this purpose, often in front

  of a ``gearbox serve`` that somehow is wrapped as a service.

The best option depends on what you are familiar with and the requirements for

performance and stability. Also, keep in mind that Kallithea mainly is serving

dynamically generated pages from a relatively slow Python process. Kallithea is

also often used inside organizations with a limited amount of users and thus no

continuous hammering from the internet.

.. _Python: http://www.python.org/

.. _Gunicorn: http://gunicorn.org/

.. _Waitress: http://waitress.readthedocs.org/en/latest/

.. _Gearbox: http://turbogears.readthedocs.io/en/latest/turbogears/gearbox.html

.. _PyPI: https://pypi.python.org/pypi

.. _Apache httpd: http://httpd.apache.org/

.. _mod_wsgi: https://code.google.com/p/modwsgi/

.. _isapi-wsgi: https://github.com/hexdump42/isapi-wsgi

.. _uWSGI: https://uwsgi-docs.readthedocs.org/en/latest/

.. _nginx: http://nginx.org/en/

.. _iis: http://en.wikipedia.org/wiki/Internet_Information_Services

.. _pip: http://en.wikipedia.org/wiki/Pip_%28package_manager%29

.. _WSGI: http://en.wikipedia.org/wiki/Web_Server_Gateway_Interface

.. _HAProxy: http://www.haproxy.org/

.. _Varnish: https://www.varnish-cache.org/

.. _npm: https://www.npmjs.com/